Mechanisms and processing limits in laser thermochemical machining

Metallic microparts can be produced with high quality by laser thermochemical machining when the etching liquid is injected coaxially to the laser beam directly into the irradiated area. The basic mechanisms and limits of the process are described. It is shown that the reaction is temperature driven independent of the laser wavelength. A limiting factor is the diffusion of the anions identified by comparing experimentally determined and calculated diffusion coefficients for the reaction products. The machining quality with respect to aspect ratio, edge radius and roughness can be enhanced by increasing the velocity of the etching liquid.